This investigation is principally aimed at studying the exchange reactions of organomercurials. Particular emphasis will be placed upon methylmercury compounds that are bonded to sulfur. The relative rate of alkyl and ligand exchange for R-Hg-SR derivatives will be studied. The study will be extended to include biologically important compounds that contain the -SH and -S-S-functional groups. The mode of reaction of these compounds with RHgX and HgX2 will be studied. The relative reactivity of CH3Hg ion to a series of ligands containing minus CR3, minus NR2, minus OR and minus SR will be determined by nmr and chromatography techniques. The experimental data will be supplemented by theoretical calculations. We will also continue our studies on the cleavage reactions of the C-Hg bond. Our conclusions will be related to the existing ecological problems associated with mercury contamination of the environment.